Prevalence of swallowing disorder in different dementia subtypes among older adults: a meta-analysis

Background: Ageing process and abnormal protein accumulation in dementia damage neural pathways affecting the swallowing process and leading to swallowing disorder. Objective: To estimate the prevalence of swallowing disorder among older adults with different dementia subtypes. Methods: We conducted a systematic search across multiple databases, including PubMed, Embase, Scopus, Web of Science and OVID Medline. The meta-analysis employed R (version 4.0.2) and utilised a generalised linear mixed model with a random-effect approach to estimate the pooled prevalence of swallowing disorder among older adults, considering various dementia subtypes. The quality of included studies was assessed using Hoy's criteria. Heterogeneity was identified through Cochrane's Q and I² statistics. To further explore heterogeneity, moderator analysis was performed to identify the contributing variables among the included studies. Results: Eighteen studies with 12, 532 older adults with different dementia subtypes were enrolled in our meta-analysis. The pooled prevalence of swallowing disorder among older adults with dementia was 58%, with 46.5% for Alzheimer's dementia, 34.9% for Parkinson's dementia, 18.8% for vascular dementia, 16.3% for mixed dementia and 12.2% for Lewy body dementia. According to assessment tools, Alzheimer's dementia had the highest prevalence, with 58% in instrumental assessments and 39% in clinical assessments. Medical history, Alzheimer's dementia, moderate-to-severe Clinical Dementia Rating, delayed oral phase, delayed pharyngeal phase and poor tongue motility contributed to the heterogeneity of the included studies. Conclusions: More than half of older adults with dementia demonstrate to have swallowing disorder. Our findings offer valuable insights to healthcare professionals for the identification of swallowing disorder in ageing population with dementia.